1. Field of the Invention
The present invention relates to a matrix display panel having a thin film transistor and, more particularly, to a liquid crystal matrix display panel to display a television image or the like.
2. Related Background Art
Hitherto, there has been proposed the display panel for displaying a multivalue image, for example, a television image by use of a high-density twodimensional matrix type liquid crystal panel (active matrix type liquid crystal panel) using thin film transistor (hereinafter, abbreviated to a TFT).
As a method of driving such a display panel, the image signal corresponding to all pixels in the horizontal direction is sampled and held within one horizontal scanning interval, and thereafter a vertical scanning signal (hereinafter, abbreviated to a gate pulse) is supplied to the gate line of the TFT, thereby allowing the image signal to be transferred to an equivalent capacitance of a liquid crystal cell and allowing the television image or the like to be displayed on the liquid crystal panel.
In the above-mentioned driving method, when the television signal is of the NTSC system, one horizontal scanning interval is 63.5 .mu.sec and the interval (horizontal blanking interval) other than the image information in one horizontal scanning interval is about 11 .mu.sec, so that the maximum width of the gate pulse of the TFT is limited to the value which is almost as long as the horizontal blanking interval. Therefore, in the case of this gate pulse width, the image signal cannot be sufficiently transferred to the liquid crystal cell due to variations in characteristics (particularly, ON resistance) of the TFT of the matrix substrate, so that a variation in luminance of the liquid crystal panel occurs. In recent years, the area of the panel enlarges more and more, the pitch of the panel becomes finer and finer, the dimension of the TFT is miniaturized, and the wiring pattern becomes fine, so that its impedance also increases. Consequently, in the case of the above gate pulse width, a sufficient charging rate into the equivalent capacitance of the liquid crystal cell can barely be obtained. Further, in order to narrow the amplitude of the image signal, the method whereby a voltage of the phase opposite to the image signal is applied to the opposite common electrodes has been also considered. However, in this case, it is necessary invert the common electrodes after the first gate pulse was applied, so that the condition concerned with the allowable time becomes severe. As described above, according to the liquid crystal display panel based on the conventional system, the lack of luminance and the variation in luminance are likely to occur, resulting in the deterioration in image quality in the recent panel of a large area and a high fine pitch.